The present invention relates to a method of fabricating a surface-emission type light-emitting device which emits light in a direction perpendicular to a substrate. The present invention also relates to a surface-emitting semiconductor laser fabricated by the above fabrication method which has stable characteristics during driving, and a method of fabricating the same. Furthermore, the present invention relates to an optical module and an optical transmission device using the surface-emitting semiconductor laser.
A surface-emission type light-emitting device represented by a surface-emitting semiconductor laser is a two-dimensionally integratable light-emitting device. Therefore, application of the surface-emission type light-emitting device to a wide range of fields such as a light source for high-speed, large-capacity optical communications has been expected.
Parasitic capacitance of the device causes a problem when driving a light-emitting device at a high speed. In the case of a surface-emitting semiconductor laser, current must be injected into an active layer from the surface of a substrate in order to drive the device. In order to prevent current from being injected into the active layer from sections other than a light-emitting section (section contributing to emission of light), an insulating layer is generally formed in a region other than near the light-emitting section. An electrode is formed on the surface of the substrate through the insulating layer. Therefore, a layer structure consisting of the electrode, insulating layer, and semiconductor is formed in the device. This layer structure causes parasitic capacitance to occur.
This parasitic capacitance is decreased by increasing the thickness of the insulating layer. Therefore, a method of filling the periphery of the light-emitting section with an insulating resin represented by a polyimide and using the resin as the insulating layer has been employed. A surface-emitting semiconductor laser having such a structure is disclosed in “Technical Report of IEICE”, LQE98-141, 1999-2 published by the Institute of Electronics, Information and Communication Engineers.
An example of a common surface-emitting semiconductor laser in which the periphery of the light-emitting section is filled with a resin and a method of fabricating the same is shown in FIGS. 17 to 19. In a surface-emitting semiconductor laser 500 shown in FIG. 17, an active layer 105 is formed in a column-shaped section 110 and light is emitted from a light exit port 116 on the upper surface of the column-shaped section 110. In order to drive the surface-emitting semiconductor laser 500, an electrode 113 for injecting current into the active layer 105 must be formed over the column-shaped section 110, as shown in FIG. 17. The periphery of the column-shaped section 110 may be filled with an insulating resin layer 517 in order to decrease the parasitic capacitance of the device, as shown in FIG. 17. When forming the surface-emitting semiconductor laser 500 shown in FIG. 17, after filling the periphery of the column-shaped section 110 with a resin layer 517a, the resin layer 517a is removed in the area formed over the column-shaped section 110, and an upper electrode 113 must be formed so as to be connected to the upper surface of the column-shaped section 110. Therefore, after filling the periphery of the column-shaped section 110 with the resin layer 517a, a device 500a is installed in a polishing machine 550 and the resin 517a is polished using abrasives 551 using a CMP process or the like before forming the upper electrode 113, as shown in FIG. 19, whereby the resin layer 517a is removed in the area formed over the column-shaped section 110.
However, the method shown in FIG. 19 may cause the column-shaped section 110 to be polished at the same time as the resin layer 517a. In this case, the device may be damaged or characteristics of the device may deteriorate. Moreover, the resin or abrasive removed by polishing may adhere to the device, thereby causing characteristics of the device to deteriorate. Therefore, it is difficult to obtain a device having stable characteristics unless the electrode 113 is formed after cleaning the upper surface of the column-shaped section 110 using a thorough cleaning step and dry etching step in combination in addition to the polishing step. The addition of the cleaning step increases the number of steps, thereby increasing the fabrication cost.